1. Field of the Invention
The present invention relates to an image forming apparatus having an operating system (OS) and a Redundant Array of Inexpensive/Independent Disks (RAID) control unit, and relates to an access request arbitration method for a RAID control unit.
2. Description of the Related Art
In a RAID system, a plurality of hard disk drives (HDDs) can be configured to appear as a single drive to an OS. This virtual single drive may comprise a plurality of logical drives. For example, a plurality of HDDs can form a logical disk in a striping mode (RAID-0 mode) providing high-speed data access or can form a logical disk for a mirroring mode (RAID-1 mode) providing improved reliability.
However, when two HDDs comprise multiple logical disks operating in a RAID-0 mode and a RAID-1 mode, for example, the two HDDs are accessed in parallel in both modes. Therefore, it is not possible to access the two HDDs via both of the modes at the same time. On the other hand, the OS recognizes the HDDs as separate logical disks for RAID-0 mode and RAID-1 mode, resulting in conflicting access requests. However, since there has been no technique for performing arbitration to resolve such access conflicts, it may happen that conflicting access requests are rejected and that an access request in the RAID-0 mode for high-speed access is given a low priority.